Jamieson, Fausset and Brown on Micah 4:13

13. thresh--destroy thy foes "gathered" by Jehovah as "sheaves" (Is 41:15, 16).

thine horn--Zion being compared to an ox treading corn, and an ox's strength lying in the horns, her strength is implied by giving her a horn of iron (compare 1Ki 22:11).

beat in pieces many--(Da 2:44).

I will consecrate their gain unto the Lord--God subjects the nations to Zion, not for her own selfish aggrandizement, but for His glory (Is 60:6, 9; Zec 14:20, with which compare Is 23:18) and for their ultimate good; therefore He is here called, not merely God of Israel, but "Lord of the whole earth."